LA5744TP-FA-E [ONSEMI]

Separately-Excited Step-Down Switching Regulator (Variable type), IPAK5 / TP5H, 500-BLKBG;


型号：	LA5744TP-FA-E
厂家：	ONSEMI
描述：	Separately-Excited Step-Down Switching Regulator (Variable type), IPAK5 / TP5H, 500-BLKBG
文件：	总5页 (文件大小：69K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

Ordering number : ENA0647A

LA5744TP

Monolithic Linear IC

Separately-Excited Step-Down

http://onsemi.com

Switching Regulator

(Variable Type)

Overview

The LA5744TP is a separately-excited step-down switching regulator (variable type).

Functions

• High efficiency.

• Time-base generator (300kHz) incorporated.

• Current limiter incorporated.

• Thermal shutdown circuit incorporated.

• Soft start circuit incorporated.

Specifications

Maximum Ratings at Ta = 25°C

Parameter

Symbol

Conditions

Ratings

Unit

Input voltage

Maximum output current

SW pin application reverse voltage

Allowable power dissipation

Operating temperature

max

-1

Pd max

Topr

Mounted on a circuit board.*

1.1

°C

-30 to +125

-40 to +150

Storage temperature

Tstg

* Specified circuit board : 76.1×114.3×1.6mm³, glass epoxy.

Stresses exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the Recommended Operating

Conditions is not implied. Extended exposure to stresses above the Recommended Operating Conditions may affect device reliability.

Recommended Operating Conditions at Ta = 25°C

Parameter

Symbol

Conditions

Ratings

Unit

Input voltage range

4.5 to 28

Semiconductor Components Industries, LLC, 2013

August, 2013

42007 MS PC 20070420-S00001 / 11707 MS PC 20061204-S00012 No.A0647-1/5

LA5744TP

Electrical Characteristics at Ta = 25°C, V = 5V

Ratings

typ

Parameter

Symbol

Conditions

Unit

min

1.20

max

1.26

Reference voltage

= 15V, I = 1.0A

1.23

Efficiency

= 15V, I = 1.0A

Switching frequency

Line regulation

Load regulation

= 15V, I = 1.0A

240

300

360

100

kHz

ΔV LINE

= 8 to 20V, I = 1.0A

ΔV LOAD

= 20V, I = 0.5 to 1.5A

Output voltage temperature

coefficient

ΔV /ΔTa

Designed target value. *

0.5

mV/°C

Ripple attenuation factor

RREJ

f = 100 to 120Hz

Current limiter operating voltage

= 15V

3.1

Thermal shutdown operating

temperature

TSD

Designed target value. *

165

°C

Thermal shutdown Hysteresis

width

ΔTSD

Designed target value. *

°C

* Design target value : No measurement made.

Package Dimensions

unit : mm (typ)

3332

Pd max -- Ta

1.4

Specified board : 114.3×76.1×1.6mm³

6.5

5.0

2.3

glass epoxy

1.2

1.1

0.5

0.8

0.6

0.4

0.6

0.2

1.2

(0.65)

1.3

0.5

0.22

0.2

--30--20

100

120

140

Ambient temperature, Ta – °C

SANYO : TP5HFA

Pin Assignment

(1) V

(2) SW

(3) GND (4) V

OUT OS

(5) SS

No.A0647-2/5

LA5744TP

Block Diagram

OUT

Constant

current

circuit

Reg.

OCP

OSC

Reset

Drive

Comp.

TSD

Amp.

ON/OFF Comp.

0.4V

VREF

GND

Application Circuit Example

22μH

OUT

LA5744TP

390μF

SBD

470μF

/50V

GND

1μF

Notes :

1. C3 is for the soft start function. Delete C3 and keep the SS pin open when the soft start function is not necessary.

2. In some cases, the output may not turn on if power is applied when a load is connected. If this is a problem, increase the value of

the inductor.

No.A0647-3/5

LA5744TP

Protection Circuit Functional Descriptions

1. Overcurrent protection function

The overcurrent protection function detects, on a cycle-by-cycle basis, the output transistor current and turns off that

output transistor current if it exceeds 3.1A.

Limit current

Inductor current

OUT

voltage

2. Short circuit protection function

This IC prevents the current from increasing when the outputs are shorted by setting the switching frequency to 30kHz

if the V

pin voltage falls below 0.8V.

Note 3 : If the soft start function is not used, the IC will start up with the overcurrent protection function operating. At this

time, the switching frequency will be cut in half. This means that the switching frequency will be 15kHz at

startup.

Note 4 : Since the switching frequency becomes 30kHz when the V pin voltage falls under 0.8V, the current capacity is

reduced. If a load is applied with the V pin voltage over 0.8V, the inductance value operates at 22μH. If a load

is to be applied when this voltage is under 0.8V, the inductance value must be increased.

Description of Functional Settings

1. Calculation equation to set the output voltage

This IC controls the switching output so that the V

The equation to set the output voltage is as follows :

pin voltage becomes 1.23V (typ).

= 1+

× 1.23V(typ)

The V

values are large.

pin has the inrush current of 1μA (typ). Therefore, the error becomes larger when R1 and R2 resistance

2. Startup Delay Function

The output voltage rises when the internal voltage reaches 0.4V (typical). Until that point, a capacitor is charged from

an internal 10μA (typical) constant-current supply. The startup delay time can be calculated as shown below

Example : Assume a 1μF capacitor is used.

C × V 1μF × 0.4

Td =

= 40 ms

10μA

No.A0647-4/5

LA5744TP

Timing Chart

voltage

30kHz

300kHz

OUT

1.23V

0.8V

voltage

ON Semiconductor and the ON logo are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC owns the rights to a number

of patents, trademarks, copyrights, trade secrets, and other intellectual property. A listing of SCILLC’s product/patent coverage may be accessed at

www.onsemi.com/site/pdf/Patent-Marking.pdf. SCILLC reserves the right to make changes without further notice to any products herein. SCILLC makes no

warranty, representation or guarantee regarding the suitabilityof its products for any particular purpose, nor does SCILLC assume any liability arising out of the

application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation special, consequential or incidental

damages. “Typical” parameters which may be provided in SCILLC data sheets and/or specifications can and do vary in different applications and actual

performance may vary over time. All operating parameters, including “Typicals” must be validated for each customer application by customer’s technical

experts. SCILLC does not convey any license under its patent rights nor the rights of others. SCILLC products are not designed, intended, or authorized for use

as components in systems intended for surgical implant into the body, or other applications intended to support or sustain life, or for any other application in

which the failure of the SCILLC product could create a situation where personal injury or death may occur. Should Buyer purchase or use SCILLC products for

any such unintended or unauthorized application, Buyer shall indemnify and hold SCILLC and its officers, employees, subsidiaries, affiliates, and distributors

harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or

death associated with such unintended or unauthorized use, even if such claim alleges that SCILLC was negligent regarding the design or manufacture of the

part. SCILLC is an Equal Opportunity/Affirmative Action Employer. This literature is subject to all applicable copyright laws and is not for resale in any manner.

PS No.A0647-5/5

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